KR101181626B1 - Method for controlling transmission power for wireless base station, and wireless base station - Google Patents

Abstract

An object of the present invention is to improve the throughput of communication between the radio base station 2 and the radio terminal 3. For that purpose, the radio base station 2 of the present invention exceeds the lower limit of the above range among the plurality of radio terminals 3 corresponding to the signal quality information belonging to the range in which the transmission scheme to be selected does not change, and the range Reduce and control the transmission power of the first wireless terminal 3 corresponding to the signal quality information below the first threshold value smaller than the upper limit of the signal within the range in which the transmission scheme does not change, and correspond to the signal quality information above the first threshold value. The transmission power of the second wireless terminal 3 is controlled to increase so that a transmission scheme with better transmission efficiency is selected.

Description

Transmission power control method of wireless base station and wireless base station {METHOD FOR CONTROLLING TRANSMISSION POWER FOR WIRELESS BASE STATION, AND WIRELESS BASE STATION}

The present invention relates to a transmission power control method of a wireless base station and a wireless base station. The present invention is preferably used in, for example, a radio communication system in which a modulation scheme, an error correction coding rate, or the like used for communication between a radio terminal and a radio base station is changed according to the signal quality of a radio section.

In a wireless communication system having a base station (BS) and a mobile station (MS), the MS can communicate with another MS, a wired terminal, a server, or the like through the BS.

As one of the wireless communication systems, there is a WiMAX system based on a method called World Wide Interoperability for Microwave Access (WiMAX), which is being developed recently. In this WiMAX system, Orthogonal Frequency Division Multiplexing (OFDMA) and Adaptive Modulation and Coding (AMC) systems are employed to improve communication efficiency.

The radio frame used in the WiMAX system includes a subframe (DL subframe) of the downlink (DL) in the direction from the BS to the MS, and a subframe (UL subframe) of the uplink (UL) in the direction from the MS to the BS. Time multiplexed.

The DL subframe further includes a preamble, a frame control header (FCH), a map information of a DL (DL map), and a map information of a UL in a two-dimensional region in the time axis (symbol time) direction and the frequency axis (sub channel frequency) direction. (UL map) (hereinafter sometimes referred to as header information), one or more DL bursts are multiplexed, and one or more UL bursts are multiplexed in the UL subframe. In addition, "burst" means the radio resource (communication area) specified by the sub-channel frequency and time (transmission timing).

Here, the preamble is an area (field) into which frame synchronization information is inserted, and the FCH is an area into which information defining map information such as the size and position of the map information is inserted. In addition, the map information includes the ID (CID) of the communication connection transmitted in the burst, the arrangement position (burst position) of the burst in the radio frame, the size of the burst (burst size), and the modulation scheme of the burst (QPSK, 16QAM). , 64QAM, etc.), code rate, transmission power control information (boost up and down), and the like.

That is, the map information can be positioned as information (burst allocation information) that designates (assigns) an area (receive area and transmission area) of a radio frame to be received and transmitted by the MS. The burst position can be specified by the symbol offset and the subchannel offset from the head symbol of the radio frame, and the burst size can be specified by the number of symbols and the number of subchannels.

Accordingly, the MS establishes radio frame synchronization of the DL and UL by detecting the preamble, and demodulates the DL burst region designated by the DL map into a demodulation scheme corresponding to a modulation scheme, a coding rate, etc. designated by the DL map, a decoding rate, and a decoding rate. By performing the decoding process, it is possible to selectively receive and process DL bursts to the MS, and to perform data transmission to the BS in the UL burst region designated by the UL map.

In addition, the MS measures the communication quality (receive quality) in the radio section with the BS, and the measurement result (receive quality information, for example, Signal to Interference and Noise Ratio, etc.) to the BS periodically or irregularly. The BS may adaptively control a modulation scheme and a coding rate for each burst based on the reception quality information from the MS. This is called AMC (Adaptive Modulation and Coding).

In addition, as a method of power allocation in an OFDMA system, a method of selecting a transmission power level for each radio unit in response to the CQI of each radio unit is described in Patent Document 1 below.

Further, Patent Document 2 discloses a method for allocating subcarriers to subchannels assigned to at least one user in a multi-user telecommunication system using a plurality of subcarriers, wherein the quality is detected for each subchannel, and this quality is determined. A method of allocating subchannels to subcarriers according to levels is described.

[Patent Document 1] Japanese Patent Application Laid-Open No. 2004-129241

[Patent Document 2] Japanese Unexamined Patent Publication No. 2006-50615

The AMC control will be described with reference to FIGS. 7 and 8. 7 is a diagram illustrating throughput characteristics of DL according to each modulation scheme and coding rate, and FIG. 8 is a diagram for explaining an example of AMC control.

As shown in Fig. 7, when the SINR is the horizontal axis and the throughput is the vertical axis, the relationship between the SINR and the throughput is in the form of a step, and the communication environment (the reception quality information in the MS) in the radio section between the MS and the BS is shown. Thus, there is a preferred modulation scheme and coding rate. For example, as shown in FIG. 8, when SINR (dB) which is reception quality information from an MS is a value more than A and less than B, BS shows the throughput (kbps) characteristic of symbol a in FIG. 16QAM (1/2) (indicated code rate in parentheses) is selected.

Similarly, when the SINR from the MS is a value greater than or equal to B in FIG. 8 and less than C, the BS selects 16QAM (3/4) representing the throughput characteristic of the symbol b in FIG. 7, and the SINR from the MS is shown in FIG. 8. In the case of the value of C or more in the figure, 64QAM (2/3) representing the throughput characteristic of the symbol c is selected from FIG. 7.

In this way, the BS selects an appropriate modulation method and coding rate according to the communication environment with the MS, and performs data transmission to the MS.

Here, for example, in the MSs reporting SINRs in the range of A≤SINR <B in FIGS. 7 and 8, the MSs reporting SINRs close to B which is the upper limit of the ranges are only slightly improved. As a result, it can be seen that the modulation scheme (coding rate) selected in the BS ranges from 16QAM (1/2) to 16QAM (3/4), so that a significant increase in throughput can be expected.

Similarly, among the MSs reporting SINRs in the range of B ≦ SINR <C in FIGS. 7 and 8, the MSs reporting an SINR close to C, which is the upper limit of the range, only slightly improves the SINR. The modulation scheme (coding rate) selected is 16QAM (3/4) to 64QAM (2/3), so that a significant increase in throughput can be expected.

Therefore, as for the MS reporting the SINR near the boundary where the modulation scheme (coding rate) selected in the BS is changed as described above, a significant increase in throughput can be expected if the SINR measured by the MS can be improved. have.

Therefore, since the reception SINR at the MS can be improved by increasing the transmission power from the BS, it is conceivable to increase (boost up) the transmission power of the DL burst before the MS on the BS side.

However, in order to realize such transmission power increase control, there are the following problems.

That is, in the radio frame, the sum of the transmission power directions in any symbol (time) in the frequency axis (subcarrier frequency) direction has an upper limit due to legal restrictions, restrictions on the transmission amplifier, etc. When the burst is allocated so that all of the subcarriers in the axial direction are used, and the transmission power reaches the above upper limit, it is impossible to perform the transmission power increase control as described above.

The present invention was devised in view of the above problems, and one of the objects thereof is to improve the throughput of communication between a wireless base station and a wireless terminal.

Moreover, it is not limited to the said objective, It is also an effect of operation | induced by each structure shown by the best form for implementing the below-mentioned invention, It is also another thing of this invention to show the action effect which is not obtained by the prior art. Positioning can be done as one of the purposes.

In order to achieve the above object, in the present invention, the following transmission power control method of a wireless base station and a wireless base station are used. In other words,

(1) A transmission power control method of a wireless base station of the present invention selects one of a plurality of transmission schemes having different transmission efficiencies for the wireless terminal according to signal quality information between the wireless terminal, and transmits to the wireless terminal. A transmission power control method of a wireless base station for transmitting a signal, the wireless base station acquiring signal quality information between a plurality of wireless terminals and corresponding to the signal quality information belonging to a range in which a transmission scheme to be selected does not change. Among the plurality of wireless terminals, the transmission power of the first wireless terminal exceeding the lower limit of the range and corresponding to the signal quality information below the first threshold value smaller than the upper limit of the range is not changed in the transmission method. Reduce and control the transmit power of the second wireless terminal corresponding to the signal quality information equal to or greater than the first threshold; The increase control is performed such that a transmission method having a higher transmission efficiency is selected than a transmission method selected by the signal quality information of one threshold or more.

(2) Here, the wireless base station exceeds the lower limit of the range in which the transmission method does not change, and corresponds to signal quality information between the second threshold value and the first threshold value smaller than the first threshold value. The reduction power of the transmission power of the first wireless terminal is controlled.

(3) In addition, the radio base station may transmit the signal transmitted to the first radio terminal and the signal transmitted to the second radio terminal in multiple times at an arbitrary symbol time.

(4) The wireless base station may also perform the increase control in a range in which the sum of the transmission powers in the frequency axis direction at any symbol time does not exceed the allowable transmission power.

(5) The wireless base station further includes a sum of an increase amount of transmission powers of the plurality of second radio terminals by the increase control, and a decrease amount of transmission powers of the plurality of first radio terminals by the reduction control. The control may be performed at or below the sum of.

(6) The signal quality information may be received signal quality information measured and reported by the wireless terminal.

(7) Alternatively, the signal quality information may be received signal quality information measured based on the received signal from the wireless terminal.

(8) In addition, the wireless base station of the present invention selects one of a plurality of transmission schemes having different transmission efficiencies with respect to the signal quality information between the wireless terminal, and transmits to the wireless terminal. A wireless base station to perform, comprising: signal quality information acquiring means for acquiring signal quality information between a plurality of wireless terminals and a plurality of wireless terminals corresponding to the signal quality information belonging to a range in which the transmission scheme to be selected is not changed; Reducing and controlling the transmission power of the first wireless terminal exceeding the lower limit of the range and corresponding to the signal quality information below the first threshold value smaller than the upper limit of the range in a range where the transmission scheme does not change, and the first Signal quality information equal to or greater than the first threshold is determined by transmitting power of a second wireless terminal corresponding to signal quality information equal to or greater than a threshold. Transmission efficiency than the transmission scheme to be selected by and a control means for controlling such that a high increase in transmission scheme selection.

(9) Here, the control means corresponds to a signal quality information between the second threshold value and the first threshold value exceeding a lower limit of the range in which the transmission method does not change and smaller than the first threshold value. The transmission power of the first wireless terminal may be controlled to be reduced.

(10) The control means may perform a frequency multiplexing of the transmission signal to the first radio terminal and the transmission signal to the second radio terminal at an arbitrary symbol time.

(11) The control means may perform the increase control in a range in which the sum of the transmission powers in the frequency axis direction at any symbol time does not exceed the allowable transmission power.

(12) The control means may further include a sum of an increase amount of the transmission powers by the increase control for the plurality of second wireless terminals, and a decrease amount of the transmission powers by the decrease control for the plurality of first wireless terminals. The control may be performed at or below the sum of.

(13) Moreover, the transmission power control method of the wireless base station of this invention is a transmission power control method of the wireless base station which selects a transmission method according to the signal quality information with a wireless terminal, and transmits to the said wireless terminal, The wireless base station acquires signal quality information between a plurality of wireless terminals, and the position in the range of the signal quality information among the wireless terminals corresponding to the signal quality information of the range in which the selected transmission scheme does not change. Therefore, the distribution of the transmission power to each wireless terminal is controlled so that the transmission scheme to at least one wireless terminal is a transmission scheme having a higher transmission efficiency than the transmission scheme selected by the signal quality information.

(14) The wireless base station of the present invention further increases the transmission power of at least the first wireless terminal among the plurality of wireless terminals in which the reception quality information is within a predetermined range, so that the reception quality exceeds the predetermined range. Transmit power by a first transmission method having a higher transmission efficiency than the second transmission method, and at least a second wireless terminal among the plurality of wireless terminals maintains the reception quality within the predetermined range. And a transmission unit for transmitting data by the second transmission method by setting the time interval between the transmission period according to the first transmission method and the transmission period according to the second transmission method.

According to the present invention described above, any one of the effects or advantages described below is obtained.

(1) The radio base station acquires signal quality information between a plurality of radio terminals and exceeds the lower limit of the range among the plurality of radio terminals corresponding to the signal quality information belonging to a range in which the transmission scheme selected by the radio base station does not change. In addition, the transmission power of the first wireless terminal corresponding to the signal quality information less than the first threshold value smaller than the upper limit of the range is reduced and controlled in a range in which the transmission method does not change, and the signal quality equal to or greater than the first threshold value. Since the transmission power of the second wireless terminal corresponding to the information is increased and controlled so that a transmission method with better transmission efficiency is selected, communication with the wireless terminal can be realized by a better transmission method without large-scale device change. Therefore, it becomes possible to improve the transmission efficiency (throughput) of the wireless communication system.

(2) In addition, the radio base station exceeds the lower limit of the range in which the transmission method does not change, and corresponds to the signal quality information between the second threshold value and the first threshold value smaller than the first threshold value. Since the transmission power of the first radio terminal is controlled to be reduced, the transmission power can be controlled efficiently, and the throughput of the radio communication system can be improved more effectively.

(3) In addition, when the radio base station transmits the signal transmitted to the first radio terminal and the signal transmitted to the second radio terminal at an arbitrary symbol time by multiplexing the frequency, the radio base station can more efficiently generate the burst of the radio frame. Since it is available, it becomes possible to improve the transmission efficiency of a wireless communication system.

(4) In addition, if the sum of the transmission powers in the frequency axis direction at any symbol time does not exceed the allowable transmission power, the wireless base station performs the apparatus configuration in the wireless base station. Since the said effect can be acquired without changing, it becomes possible to aim at cost reduction.

1 is a block diagram showing a configuration of main parts of a wireless communication system according to an embodiment of the present invention.
FIG. 2 is a block diagram showing the configuration of a BS (DL / UL map generation unit) shown in FIG. 1; FIG.
3 shows throughput characteristics of a modulation scheme and a coding rate.
4 is a diagram showing a relationship between reception quality information and an area;
5 is a diagram for explaining burst allocation of radio frames.
FIG. 6 is a flowchart for explaining an example of the operation of the BS shown in FIG. 2; FIG.
7 is a diagram illustrating throughput characteristics of a modulation scheme and a coding rate.
8 is a diagram for explaining an example of AMC control.
[Description of Symbols]
1: Wireless communication system
2: wireless base station (BS)
3: wireless terminal (MS)
4: network interface
5: BS side PDU generation unit
6: BS side transmission processing unit
7, 15: duplexer
8, 14: antenna
9: BS side receiving processing unit
10: BS side packet generation unit
11: DL / UL modulation method code rate control unit
12: DL / UL map generation unit
13: connection management unit
16: MS side receiving processing unit
17: MS side packet generation unit
18: application processing unit
19: MS-side PDU generation unit
20: MS side transmission processing unit
21: connection detail classification
22: reception quality prediction unit
23: no boost DL map generator
24: boost down DL map generation unit
25: boost up DL map generator
26: surplus power calculation unit

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, this invention is not limited to embodiment described below, Of course, it can be variously deformed and implemented in the range which does not deviate from the meaning of this invention.

[A] Description of One Embodiment

1 is a block diagram showing a configuration of main parts of a wireless communication system according to an embodiment of the present invention. The radio communication system 1 shown in FIG. 1 includes a plurality of radio terminals (MS) 3 and a radio base station (BS) 2 which performs radio communication with these MSs 3. The BS 2 performs multiplexing of transmission data to a radio frame by the OFDMA method, for example, and transmits downlink data to a plurality of MSs 3. On the other hand, the MS 3 measures signal quality information (receive quality information) (SINR, etc.) for downlink data received from the BS 2 and reports it to the BS 2.

(Description of MS (3))

The MS 3 shown in Fig. 1 focuses on the functions of the main parts thereof. For example, the antenna 14, the duplexer 15, the MS-side receiving processor 16, and the MS-side packet generator ( 17), an application processing unit 18, an MS side PDU generation unit 19, and an MS side transmission processing unit 20.

Here, the antenna 14 has a function of transmitting a radio signal of UL to the BS 2 to the BS 2 and receiving a radio signal of the DL from the BS 2.

The duplexer 15 outputs a radio signal of UL from the MS side transmission processing section 20 to the antenna 14, while the DL (including map information) received from the BS 2 through the antenna 14 is received. And a function of outputting a radio signal to the MS-side reception processing unit 16.

The MS side reception processing unit 16 performs predetermined reception processing on the reception signal from the BS 2 received from the duplexer 15. For example, the MS side reception processing unit 16 obtains map information (DL / UL map) from the reception signal. It can extract and demodulate and decode by the demodulation method and the decoding method according to the transmission method of DL bursts, such as the modulation method and coding rate specified by the DL map.

In addition, the MS side reception processing unit 16 of the present example also has a function of periodically or irregularly measuring reception quality information such as SINR based on the reception signal from the BS 2. The measured reception quality information is notified to the MS side transmission processing unit 20 together with the UL map, and transmitted from the MS side transmission processing unit 20 to the BS 2 in the UL burst specified by the UL map ( Reported).

The MS side packet generation unit 17 generates DL data (DL packets) based on the received signal from the BS 2, and the generated packets are sent to the application processing unit 18.

The application processing unit 18 generates transmission data (UL data) directed to the BS 2 according to a predetermined application process. For example, the application processing unit 18 generates a response to the DL data from the MS-side packet generation unit 17. Can be generated by UL data.

The MS side PDU generation unit 19 generates a PDU (Protocol Data Unit) based on the UL data from the application processing unit 18. This PDU is a unit of data handled by the protocol of the transmission packet. For example, the PDU of Transmission Control Protocol / Internet Protocol (TCP / IP) is a "packet", and the PDU of ATM (Asynchronous Transfer Mode) is , "Cell". At the head of this PDU, communication control information such as a header used in the protocol of the transmission data is added to the data main body.

The MS side transmission processing unit 20 performs a predetermined transmission process on the PDU from the MS side PDU generation unit 19, for example, specified by the UL map extracted by the MS side reception processing unit 16. The PDU is encoded and modulated by a coding rate and a modulation method. In addition, the MS side transmission processing unit 20 of this example also has a function of mapping the reception quality information measured by the MS side reception processing unit 16 to the UL burst specified by the UL map and transmitting it to the BS 2. have.

The MS 3 of the present example is configured as described above, so as to obtain reception quality information such as SINR based on the reception signal from the BS 2, and the BS 2 receives this reception quality information periodically or irregularly. Can be sent to (report).

(Explanation of BS (2))

On the other hand, when the BS 2 shown in Fig. 1 pays attention to the functions of its main parts, for example, the network interface 4, the BS side PDU generation unit 5, the BS side transmission processing unit 6, The duplexer 7, the antenna 8, the BS side receiving processor 9, the BS side packet generator 10, the DL / UL modulation scheme coding rate control unit 11, and DL / UL map generation. The unit 12 and the connection manager 13 are provided.

Here, the antenna 8 has a function of transmitting a radio signal of the DL to the MS 3 and receiving a radio signal of the UL from the MS 3.

The duplexer 7 outputs the DL radio signal from the BS side transmission processor 6 to the antenna 8, while the UL radio signal received by the antenna 8 is transmitted to the BS side reception processor 9. It has a function to output.

The BS side receiving processing unit (signal quality information acquiring means) 9 performs various receiving processes on signals received from the MS 3 through the antenna 8 and the duplexer 7, and is, for example, a received signal. (UL burst) is a function of demodulating and decoding (UL data) the modulation scheme designated by the UL map to the MS 3, the demodulation scheme according to the coding rate, and the decoding scheme to obtain UL data, and the UL burst (UL data) to the MS. When the reception quality information measured in (3) is included, the information is provided to the DL / UL modulation scheme coding rate control unit 11. The reception quality information may be measured based on UL data received from the BS 2 side. In this case, the measurement function can be provided in the BS side reception processing unit 9. At this time, the reception quality information measured by the BS 2 based on the UL data is the reception quality information in the up direction (receive quality information on the BS 2 side), but the communication quality is the same in the up direction and the downward direction. The reception quality information is proportional to the transmission power of the transmitting side. Accordingly, the BS 2 corrects the reception quality information on the side of the BS 2 based on the ratio of the transmission power of the BS 2 to the known transmission power of the MS 3, and thus, on the MS 3 side. The reception quality information (receiving quality information in the downward direction) may be calculated.

The BS-side packet generation unit 10 is based on the UL data from the BS-side reception processing unit 9 and the connection ID managed by the connection management unit 13, so as to be different from the IP (Internet Protocol) network or ATM network. And DL data such as a packet to be transmitted to a network (not shown) or a response packet to received UL data.

The network interface 4 has an interface function (function to perform various protocol control, etc.) with a higher network such as the IP network or ATM network described above, and UL data is transmitted to the upper network side from the MS 3 from the higher network. ) The DL data or DL data for the response to the MS 3 is transmitted to the BS-side PDU generation unit 5, respectively.

The BS side PDU generation unit 5 generates a PDU based on the DL data from the network interface 4. Apart from the data main body, communication control information such as a header used in the protocol of the DL data is added to the head of this PDU.

The connection management unit 13 manages a communication connection (CID) with the MS 3, and includes a BS side packet generation unit 10, a BS side PDU generation unit 5, and a DL / UL modulation scheme coding rate control unit. (11) performs each process (UL / DL burst mapping, transmission process, etc.) based on the management information.

The DL / UL modulation scheme coding rate control unit 11 controls (selects) the modulation scheme and coding rate of DL and UL data (burst) on the basis of the reception quality information from the BS side reception processing unit 9, i.e. It has a function of performing the AMC control described above.

In other words, the DL / UL modulation scheme coding rate control unit 11 of the present example has a function of selecting a transmission scheme of DL data to each MS 3 based on the reception quality information.

The DL / UL map generation unit 12 generates map information (DL map and UL map) under the control of the DL / UL modulation scheme coding rate control unit 11. In this example, as will be described later, DL in front of MS 3 corresponding to reception quality information (hereinafter also referred to simply as "reception SINR") near the boundary where the transmission scheme selected by BS 2 changes to a better condition when the reception quality information is improved by a certain amount. While increasing (boost up) the transmit power of the burst, the transmit power of the DL burst in front of the other MS 3 is decreased (boost down) so as not to exceed the upper limit of the transmit power in the frequency axis direction with the increase. And map information including information (such as CID of transmission target DL burst, transmission power information, etc.) for control.

In this case, preferably, information for performing control to reduce (boost down) the transmission power of the DL bursts to other MSs 3, which are assumed to be unchanged even if the transmission power is lowered (of the control target DL bursts). Map information including CID, transmission power information, etc.) is generated.

In addition, the map information is a boost up target, a boost down target, and other than them (that is, neither boost up nor boost down) in order to facilitate the boost up within a range not exceeding the upper limit of the transmission power. DL bursts are constructed (created) such that each of the DL bursts is at a predetermined position in the radio frame. Details thereof will be described later with reference to FIG. 5.

The BS side transmission processing unit 6 performs predetermined transmission processing on the DL data from the BS side PDU generation unit 5 based on the DL map generated by the DL / UL map generation unit 12, For example, a function of encoding and modulating the DL data by a coding rate specified by the DL map and a modulation scheme, and the transmission power of the DL burst based on the CID and the transmission power information included in the DL map. Control function (boost up or boost down).

In addition, the BS side transmission processing unit (transmitter) 6 of this example is the MS (3) to be subjected to the reduction control (boost down) of the transmission power in the DL / UL map generation unit 12 as described later. 1) DL data to the future, DL data to the MS 3 (second wireless terminal) targeted to increase (boost up) and control the transmission power in the DL / UL map generation unit 12, and The other DL data is provided with a function of mapping the DL bursts of the radio frame so as to be in the predetermined arrangement specified by the DL map.

The BS 2 according to the embodiment of the present example is configured as described above, so as to adaptively change a transmission scheme such as a modulation scheme and a coding rate of a DL burst to the MS 3 in accordance with the reception quality information ( Can be transmitted to the MS 3, and the transmission scheme selected by the BS 2 changes to a condition in which transmission efficiency is better due to a slight increase in transmission power. By allowing the transmission power to be boosted up preferentially, the above better conditions can be selected in the BS 2. Therefore, the throughput of the DL can be improved.

(Detailed description of the DL / UL map generator 12)

Next, the configuration and operation of the above-described DL / UL map generation unit 12 will be described with reference to FIGS. 2 to 6.

FIG. 2 is a block diagram showing the configuration of the DL / UL map generation unit 12 shown in FIG.

As shown in FIG. 2, the DL / UL map generator 12 of this example includes a connection detail classifier 21 having a reception quality predictor 22, a boostless DL map generator 23, and the like. And a boost down DL map generation section 24, a boost up DL map generation section 25, and a surplus power calculation section 26.

Here, the connection detail classifying unit 21, in cooperation with the connection management unit 13, receives the reception quality information (or the reception quality measured by the BS 2 side) reported from the MS 3 for each CID of the received UL burst. Information), a function of selecting a modulation scheme and a coding rate by a selection table equivalent to the selection table shown in FIG. 8 based on the reception quality information, and the MS (based on the reception quality information). 3) (CID), for example, as shown in Figs. 3 and 4, three areas in which 16QAM (3/4) is selected are divided into three areas, i.e., (1 ) B≤SINR <B1, (2) B1≤SINR <B2, and (3) B2≤SINR <C.

Here, these areas (1), (2) and (3) mean the following, respectively.

(1) When reception quality information is deteriorated a small amount (predetermined amount), an area in which a modulation method with a lower efficiency (throughput) and a coding rate are selected

(2) Even if the reception quality information is changed (deteriorated or improved) by the predetermined amount, the same modulation scheme and code rate (modulation scheme 16QAM, code rate 3/4 here) is selected.

(3) When the reception quality information is slightly improved, an area in which a higher throughput modulation scheme and coding rate (for example, modulation scheme 64QAM and coding rate 2/3) are selected.

In addition, since the reception quality information measured by the MS 3 can be changed by changing the transmission power of the DL burst from the BS 2, the above areas (1), (2) and (3) are as follows. It can also be understood as meaning.

(1) When the transmission power of the DL burst is reduced by a small amount (a predetermined amount), a region having a lower efficiency modulation method and a coding rate is selected.

(2) Even if the transmission power of the DL burst is increased a small amount, a more efficient modulation method and a coding rate cannot be selected, and even if the transmission power is reduced a small amount, a less efficient modulation method and a coding rate are not selected. Area

(3) By increasing the transmission power of the DL burst by a small amount, a more efficient modulation method and an area where a coding rate can be selected

Therefore, the connection detail classification unit 21 holds the classification (selection) table (selection information of the transmission method) as shown in FIG. 4 as a data in a table format, for example, in a memory not shown. The table can also be generated from information (which may be a theoretical value or an actual value) showing the relationship between SINR and throughput shown in FIG. 4.

In the above example, the modulation scheme 16QAM is a region sandwiched between a threshold for determining a modulation scheme and a coding rate (the region in which an arbitrary modulation scheme and an error coding rate are selected when reception quality information is present therebetween). Although classification (segmentation) has been performed for an area having a code rate of 3/4, similar classification (segmentation) can be performed for all or part of the available modulation schemes and code rates.

In addition, when the reception quality predicting unit 22 performs a predetermined amount of boost up or boost down on each MS 3, how the SINR reported from each MS 3 changes (that is, the SINR change). This function has a function of predicting which modulation scheme and coding rate is selected and how much the throughput of the DL changes. This prediction is realized by, for example, simulation of a wireless communication system. And based on the prediction result, each MS 3 belongs to which area (1), (2), and (3) mentioned above, and it is the target of a boost up, a boost down, and others (no boost). MS 3 (CID) is determined.

The no-boost DL map generation unit 23 generates DL map information for the MS 3 determined as the no-boost target, that is, the MS 3 belonging to the region 1 (B≤SINR <B1). .

The boost down DL map generation unit 24 is a DL for the MS 3 determined as the boost down target, that is, the MS 3 (first wireless terminal) belonging to the region 2 (B1 ≦ SINR <B2). To generate map information. This DL map information includes information such as a CID, a DL burst position, a transmission power after boosting down (may be a reduction in transmission power), a modulation method, a coding rate, and the like, and based on the information, the BS side transmission processing unit ( In 6) boost down (transmission power reduction) control of the DL burst is performed.

The surplus power calculation unit 26 calculates surplus power in the frequency axis direction in the radio frame based on the respective DL map information generated by the no boost DL map generation unit 23 and the boost down DL map generation unit 24. It is.

The boost-up DL map generation section 25 is a DL for the MS 3 determined as the boost-up target, that is, the MS 3 (second wireless terminal) belonging to the region 3 (B2? SINR <C). Map information is generated, and at this time, the boost up width of the target DL burst and the mapping position to the radio frame can be determined so as not to exceed the surplus power. The DL map information here also includes information such as a CID, a DL burst position, a transmission power after boost up, a modulation scheme, a coding rate, and the like, and the BS side transmission processing section 6 boosts the DL burst based on the information. (Transmission power increase) control is performed.

In this way, the DL / UL map generation unit 12 includes the MS 3 (first wireless terminal) belonging to the area 2 (B1 (second threshold value) ≤ SINR <B2 (first threshold value)). The transmission power of the MS 3 (second wireless terminal) belonging to the area 3 (B2 (first threshold value)? SINR <C] is reduced and controlled in a range in which the transmission method does not change. It has a function as a control means for increasing and controlling to select a transmission method with better transmission efficiency.

In other words, the BS 2 of the present example having the DL / UL map generation unit 12 receives a range in which the transmission method selected by the reception quality information does not change (in the above example, B ≦ SINR <C). The transmission method to the at least one BS 2 is better than the transmission method selected by the reception quality information according to the position of the reception quality information of the MS 3 corresponding to the quality information in the above range. It is provided with the function which controls distribution of the transmission power to each said MS 3 so that it may become.

Further, in another example, part of the MS 3 belonging to [B2 (first threshold value) ≤ SINR <C] changes the transmission method to a faster transmission method by boosting up, and then [B2 (first threshold). The other part of the MS 3 belonging to the value) < SINR &lt; C] is boosted down. Preferably, the boost down is boosted down so that the transmission scheme is not changed.

Of course, the boost up (L> 0) of one MS (3) may correspond to the boost down (-L) of one MS (3), but to the boost up (L) of one MS (3). On the other hand, L ≦ ΣNi can be realized by matching the boost down (Ni: i = 1 to M) of the plurality of MSs (M: M is a natural number of two or more).

Here, with reference to Fig. 5, the operation of generating map information (DL map information) in the boostless DL map generation unit 23, the boost down DL map generation unit 24, and the boost up DL map generation unit 25 is described. Explain. 5 is a diagram for explaining burst allocation of a radio frame.

As shown in FIG. 5, when the radio frame used for the radio communication system 1 is a radio frame conforming to the OFDMA system, the radio frame includes a header area, a DL subframe (DL signal area), The UL subframe (UL signal region) is time multiplexed, a preamble signal, an FCH, and a DL / UL map are mapped to the header region, and a time axis (symbol time) direction and a frequency axis (sub channel frequency) direction are mapped to the DL subframe. In the two-dimensional region of, a UL / DL map, one or more DL bursts are multiplexed, and one or more UL bursts are multiplexed in the UL subframe.

Firstly, the no-boost DL map generation unit 23 determines the MS 3 determined as a no-boost target, that is, a DL burst # 1 to the MS 3 belonging to the region 1 (B≤SINR <B1). As shown in Fig. 5, the maps (time multiplexing) are stacked so as to overlap in the time axis direction as vertically long bursts in which slots in the frequency axis (sub channel) direction are larger than slots in the time axis (symbol) direction, respectively. The burst allocation information is generated as no boost DL map information.

Preferably, when data is arranged in order in the frequency direction and data cannot be loaded in the frequency direction, data is sequentially arranged in the frequency direction at the next time.

Next, the boost down DL map generation unit 24 forwards the MS 3 determined as the MS 3 to be boosted down, that is, the MS 3 belonging to the region 2 (B1? SINR < B2). As shown in Fig. 5, DL bursts # 5 to # 10 overlap each other in the remaining DL signal area (empty area) as a horizontally long burst with more slots in the time axis direction than slots in the frequency axis direction, respectively. Burst allocation information for mapping (frequency multiplexing) to be accumulated is generated as boost down DL map information.

Preferably, the data is arranged in order in the time direction, and when the arrangement of the predetermined time width is completed, the data is sequentially arranged in the time direction with respect to the next frequency.

At that time, the boost down DL map generation unit 24 is capable of boosting down the transmission power in a range in which the modulation scheme selected and the coding rate do not change for the DL bursts # 5 to # 10 of the boost down target. While determining whether or not, the transmission power information to be included in the DL map information is boosted down.

Next, the boost-up DL map generation unit 25 forwards the MS 3 determined as the MS 3 to be boosted up, that is, the MS 3 belonging to the region 3 (B2? SINR <C). As shown in Fig. 5, DL bursts # 11 to # 16 map burst allocation information for mapping (frequency multiplexing) in the remaining DL signal area (empty area) so as to overlap each other in the direction of the frequency axis as a burst that is horizontally long. Generated as boost up DL map information.

Preferably, the data is arranged in the order of data in the time direction, and when the arrangement of the predetermined time width is completed, data is sequentially arranged in the time direction with respect to the next frequency.

At that time, the boost-up DL map generation unit 25, as described above, based on the surplus power calculated by the surplus power calculation unit 26, for DL bursts # 11 to # 16 to be boosted up, The transmission power at all times (symbols) does not exceed a predetermined upper limit while determining whether the modulation system with higher efficiency (throughput) and the transmission power can be boosted up until the coding rate becomes selectable. The transmission power information included in the DL map information in the range is boosted up.

In this manner, each map generator 23 to 25 performs frequency multiplexing on the signal transmitted to the first MS 3 and the signal transmitted to the second MS 3 at an arbitrary symbol time. A function of generating a map, a function of performing the increment control in a range in which the sum of the transmission powers in the frequency axis direction at an arbitrary symbol time does not exceed the allowable transmission power, and the plurality of second MSs (3). And a sum of an increase amount of the transmission powers by the increase control with respect to the &lt; RTI ID = 0.0 &gt;) &lt; / RTI &gt;

As described above, DL bursts # 5 to # 10 and # 11 to # 16 in front of the MS 3 of the boost-up and boost-down targets (ie, the transmission power control targets) are transversely long in the frequency axis direction. By multiplexing, transmission power control in the range which does not exceed the upper limit of transmission power in the same time (symbol) becomes easy. In other words, the BS 2 of the present example distributes the transmission power of the DL burst at the same time (symbol) to the MS 3 of the boost up and the boost down targets. It can be said that the control is to increase the page.

In addition, when boosting up to burst # 11 of the area | region 3, transmission power can also be suppressed by boosting down to burst # 12 and burst # 13. In this case, the area 2 may also be the same arrangement method as the area 1.

In other words, when boosting up for an arbitrary burst, if the boost is down for a burst in which part or all overlap with the burst, the transmission power in the overlapping time period can be suppressed. For example, in FIG. 5, when bursting up burst # 12, a burst in which part or all overlaps with burst # 12 is each burst except bursts # 7 and # 13. Can be a boost down target.

In other words, the BS 2 of this example includes at least the first MS 3 of the plurality of MSs 3 in which the SINR (receive quality information) falls within a predetermined range (for example, B ≦ SINR <C). In this case, the transmission power is increased to be a reception quality exceeding the predetermined range, and data is transmitted by the first transmission method (for example, 64QAM (2/3)). ), At least for the second MS 3, the transmission power is reduced to a reception quality in the predetermined range, and a second transmission method (eg, 16QAM (3/4) that is slower than the first transmission method is used. A transmission unit 6, 11, 12, 13 which transmits data by means of)), and in the radio frame shown in Fig. 5, the transmission period (1) by the first transmission method 64QAM (2/3) Symbol time) and a time zone in which the transmission period (symbol time) by the second transmission method (for example, 16QAM (3/4)) overlaps at least. There.

Therefore, the transmission power is increased and decreased as described above with respect to at least the overlapping time zones, thereby making it possible to flexibly and easily control the distribution of the transmission power, while suppressing the transmission power while the SINR exceeds the predetermined range. MS 3 can be generated. As a result, it becomes possible to improve the transmission efficiency (throughput) of the wireless communication system 1.

Next, the operation of the above-described BS 2 will be described with reference to FIG. 6. 6 is a flowchart for explaining an example of the operation of the BS 2.

As shown in FIG. 6, first, the BS side reception processing unit 9 obtains reception quality information from signals received from the MS 3 through the antenna 8 and the duplexer 7 (see step S1). The DL / UL modulation scheme coding rate control unit 11 is informed of the information.

The DL / UL modulation scheme coding rate control unit 11, based on the reception quality information received from the MS 3 from the BS side reception processing unit 9 and the reception quality information of the BS 2, performs DL and UL data ( The modulation method and the coding rate of the burst) are controlled (selected) (see step S2).

Next, when the DL / UL map generation unit 12 (connection detail classifying unit 21 and reception quality predicting unit 22) performs a predetermined amount of boost up or boost down on each MS 3, Predict how the SINR reported from each MS 3 will change (see steps S3 and S4), and based on the prediction result, the MS 3 to be boosted up, with respect to the connection with each MS 3, The MSs are classified as boost down target MSs 3 and MSs 3 other than these (ie MS 3 without boost targets) (see steps S5 to S7).

Here, the DL / UL map generation unit 12 determines (confirms) whether or not the above classification has been performed for all of the connections (see step S8), and if there are any connections not yet classified (NO in step S8). "Refer to route", when the process from step S2 to S7 is performed again, and it is determined that classification is finished for all connections (see "Yes" route in step S8), the no-boost DL map generator 23 The MS 3 determined as the no-boost target connection, in other words, generates DL map information for the MS 3 belonging to the region 1 (B≤SINR <B1), and the boost-down DL map generator 24 And DL map information for the MS 3 (the first wireless terminal) belonging to the MS 3 determined as the boost down target, that is, the area 2 (B1? SINR < B2) (see step S9). The DL map information here includes information such as the CID, the DL burst position, the modulation scheme selected in step 2, the coding rate, the transmission power after the boost down, and the like, based on the information. Boost down (transmission power reduction) control of the DL burst is performed.

The surplus power calculation unit 26 then uses surplus power in the frequency axis direction in the radio frame based on the DL map information generated by the no boost DL map generation unit 23 and the boost down DL map generation unit 24. (See step S10), the boost-up DL map generation unit 25 determines the MS 3 determined as the boost-up target, that is, the MS 3 belonging to the region 3 (B2? SINR < C) ( DL map information for the second wireless terminal) is generated (see step S11). The DL map information here also includes information such as the CID, the DL burst position, the modulation method selected in step 2, the coding rate, the transmission power after the boost-up, and the like, and the BS side transmission processing unit 6 Boost up (transmission power increase) control of the DL burst is performed.

Here, when the boost-up DL map generation unit 25 generates DL map information for the MS 3 determined as the boost-up target, the boost-up DL map generation unit 25 is based on the surplus power calculation result in the surplus power calculation unit 26. It is determined whether or not there is a beam (free) in the surplus power in the frequency axis direction in the radio frame (see step S12). In step S12, when generating the DL map information to be boosted up and determining that there is no surplus power (see no route in step S12), the BS-side PDU generation unit 5 generates a PDU (see step S13). .

Next, the BS side transmission processing unit 6 transmits DL data to the MS 3 (first radio terminal) to be boosted down and DL data to the MS 3 (second radio terminal) to be boosted up. As described above, DL data other than these are mapped to the DL bursts of the radio frame, and subjected to a predetermined radio transmission process (modulation, encoding, etc.) and transmitted to the MS 3 (see step S14). ).

And BS 2 performs AMC control according to the reception quality information reported from MS 3 after the said transmission power control (refer step S1 and S2).

As described above, according to the processing procedure shown in FIG. 6, the BS 2 can realize communication with the MS 3 by a better transmission method without performing a large-scale device change, and as a result, wireless communication It is possible to improve the transmission efficiency (throughput) of the system 1.

Further, the BS 2 performs the above increase control in a range in which the sum of the transmission powers in the frequency axis direction at an arbitrary symbol time does not exceed the allowable transmission power, so that the apparatus configuration in the BS 2 is changed. The above effects can be obtained without significantly changing, and the cost can be reduced.

[B] other

As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to said embodiment, It can implement arbitrarily modified in the range which does not deviate from the meaning of this invention.

For example, in the above embodiment, as shown in Fig. 3, transmission power control is performed for the MS 3 belonging to the modulation scheme 16QAM and the region (B≤SINR <C) of code rate 3/4. Of course, the same transmission power control can be performed for the MS 3 belonging to another area (for example, A? SINR < B, B? SINR < C).

In the above embodiment, when the reception quality predicting unit 22 performs a predetermined amount of boost up or boost down on each MS 3, it predicts how the SINR reported from each MS 3 changes. Based on this prediction result, each MS 3 is classified as to which area in Fig. 3, but a simpler classification method may be employed. For example, the area of the range of B to C in FIG. 3 is divided into three, and the classification can be performed according to which area the SINR reported from each MS 3 belongs to. In this way, since the prediction processing in the reception quality predicting section 22 can be omitted, the processing in the BS 2 can be simplified and the operation can be speeded up.

In addition, in the above embodiment, after the BS 2 preferentially boosts up the transmission power of the DL burst to the MS 3 to be boosted up, the SINR reported from the MS 3 makes transmission more efficient. Although the method is selected, for example, after the BS 2 boosts or boosts down, the transmission method of the MS 3 may be selected without waiting for the SINR report from the MS 3. For example, if the BS 2 voluntarily makes the transmission method of the MS 3 a more efficient transmission method for the MS 3 to be boosted up, the transmission method of the MS 3 can be quickly changed. Since it can select (change), it becomes possible to improve the throughput of the whole wireless communication system 1 efficiently.

In addition, this invention can be applied without being limited to the WiMAX system mentioned above. For example, the BS 2 can control the transmission power of the MS 3, select the transmission method of the MS 3, and apply it to a communication system for transmitting.

Industrial availability

As described in detail above, according to the present invention, since the transmission efficiency (throughput) of the entire wireless communication system can be improved, it is very useful in the field of wireless communication technology, for example, the field of mobile wireless communication technology having an AMC function. I think.

Claims (14)

A transmission power control method of a wireless base station, which transmits to a wireless terminal by selecting any one of a plurality of transmission schemes having different transmission efficiencies for the wireless terminal in accordance with signal quality information between the wireless terminal.
The wireless base station,
Acquires signal quality information between a plurality of wireless terminals,
Of a plurality of wireless terminals corresponding to the said signal quality information which belongs to the range which does not change the transmission system which selects, it respond | corresponds to the signal quality information below the 1st threshold exceeding the lower limit of the said range and smaller than the upper limit of the said range. Reducing and controlling the transmission power of the first wireless terminal within a range where the transmission scheme does not change, and transmitting power of the second wireless terminal corresponding to the signal quality information of the first threshold value or more to the signal quality information of the first threshold value or more. The transmission power control method of the wireless base station, characterized in that the increase control to select a transmission method having a higher transmission efficiency than the transmission method selected by the. The method of claim 1,
The wireless base station,
The transmission power of the first wireless terminal corresponding to the signal quality information between the second threshold value and the first threshold value exceeding a lower limit of the range in which the transmission method does not change and is smaller than the first threshold value is determined. A transmission power control method of a wireless base station, characterized in that the reduction control. The method of claim 2,
The wireless base station,
And transmitting a signal multiplexed to the first wireless terminal and a signal transmitted to the second wireless terminal at an arbitrary symbol time. The method according to claim 2 or 3,
The wireless base station,
And the increase control is performed in a range in which the sum of the transmission powers in the frequency axis direction at an arbitrary symbol time does not exceed the allowable transmission power. 4. The method according to any one of claims 1 to 3,
The wireless base station,
The sum of the increase amounts of the transmit powers by the increase control for the plurality of second wireless terminals is controlled to be equal to or less than the sum of the decrease amounts of the transmit powers by the decrease control for the plurality of first wireless terminals. Transmission power control method of a wireless base station. 4. The method according to any one of claims 1 to 3,
And the signal quality information is received signal quality information measured and notified by the wireless terminal. 4. The method according to any one of claims 1 to 3,
And the signal quality information is received signal quality information measured based on the received signal from the wireless terminal. A wireless base station that selects any one of a plurality of transmission schemes having different transmission efficiencies with respect to signal quality information between a wireless terminal and transmits to the wireless terminal.
Signal quality information acquisition means for acquiring signal quality information between the plurality of wireless terminals;
Of a plurality of wireless terminals corresponding to the said signal quality information which belongs to the range which does not change the transmission system which selects, it respond | corresponds to the signal quality information below the 1st threshold exceeding the lower limit of the said range and smaller than the upper limit of the said range. Reducing and controlling the transmission power of the first wireless terminal within a range where the transmission scheme does not change, and transmitting power of the second wireless terminal corresponding to the signal quality information of the first threshold value or more to the signal quality information of the first threshold value or more. Control means for increasing and controlling the transmission method having a higher transmission efficiency than the transmission method selected by
Wireless base station comprising a. 9. The method of claim 8,
Wherein,
The transmission power of the first wireless terminal corresponding to the signal quality information between the second threshold value and the first threshold value exceeding a lower limit of the range in which the transmission method does not change and is smaller than the first threshold value is determined. Wireless base station characterized in that the reduction control. 10. The method of claim 9,
Wherein,
And transmitting a signal multiplexed to the first wireless terminal and a signal transmitted to the second wireless terminal at an arbitrary symbol time. 11. The method according to claim 9 or 10,
Wherein,
And performing the increase control in a range in which the sum of the transmission powers in the frequency axis direction at any symbol time does not exceed the allowable transmission power. 11. The method according to any one of claims 8 to 10,
Wherein,
The sum of the increase amounts of the transmit powers by the increase control for the plurality of second wireless terminals is controlled to be equal to or less than the sum of the decrease amounts of the transmit powers by the decrease control for the plurality of first wireless terminals. Wireless base station. A transmission power control method of a wireless base station which selects a transmission method according to signal quality information between a wireless terminal and transmits to the wireless terminal.
The wireless base station,
Acquires signal quality information between a plurality of wireless terminals,
Among wireless terminals corresponding to signal quality information in a range in which the selected transmission scheme does not change, the transmission scheme to at least one wireless terminal is determined by the signal quality information according to the position of the signal quality information in the range. A transmission power control method for a wireless base station, wherein the distribution of transmission power to each wireless terminal is controlled so as to be a transmission method having a higher transmission efficiency than the selected transmission method. Among the plurality of wireless terminals in which the reception quality information is within a predetermined range, the transmission power is increased for at least the first wireless terminal to be a reception quality exceeding the predetermined range, so that the transmission efficiency is higher than that of the second transmission method. The data is transmitted by the first transmission method, and the transmission power is reduced so that the reception quality of the predetermined range is maintained for at least the second wireless terminal among the plurality of wireless terminals. And a transmitting unit for transmitting,
And a time period in which the transmission period according to the first transmission method and the transmission period according to the second transmission method overlap at least.

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